Dial indicator



March 16, 1937.

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Patented Mar. 16, 1937 DIAL INDICATOR James G. Sisson, Athol, Mass., assignor to The L. S. Starrett Company, Athol, Mass., a corporation of Massachusetts Application April 11, 1934, Serial No. 720,093

2 Claims.

This application relates to further improvements in dial gages or dial indicators or indicator structures.

It has for its purpose to provide a structural basis of great strength and steadiness. It also `makes possible rened and economical manufacture on factory production basis, particularly as to the improvement of guiding of the rack and the mounting of the pinions and rack between the bridge'and plate.

Throughout the specification and drawings like reference characters are employed to indicate corresponding parts:

Fig. 1 is a side view of the general type of dial gage involved. y Fig. 2 is a rear view with back plate removed. Fig. 3 is a vertical central Section.

Fig. 4 shows an enlarged View in plan of the footed bridge and fragment of rack.

Fig. 5 is a side view of the bridge member.

Fig. 6 is a similar view of the same at a different angle.

Fig. 7 is a view of the rack stem and guide bar.

Fig. 8 is a view looking down on the top bearing, and

Fig. 9 is a fragmentary section showing a modified form of bezel assembly'.

In thedial indicators according to my inven tion as shown, the casing consists of a stout tubular-shell I recessed at its front and rear edges at I1 and firmly fitted on its front by the dial plate 3 and on its rear by a solid inset back 2. The.' casing is therefore essentially a stout drum screwed together and having its inner mechanism rigidly mounted on its interior.

The bridge piece 4 is supported by the plate 3 each bracing the other and mutually cooperative to provide opposed bearings for various pinion or like elements supported by them as indicated 40 herein.

The plate. 3 isa rigid metal disc drilled for bearings for the hair spring gear shaft 50 and for that of the rack pinion 6I). At their other ends these parts journal in aligned bearings in the bridge piece 4 mentioned above. This bridge piece is flanged as at 41 and footed as at 42.

Centrally of its fiat top portion which is supported parallel to the piece 4 the bridge is opened up by a somewhat U-shaped cut 40 leaving a tongue 4I. As seen best in Fig. 4, this tongue 4I is bent downwardly as at 4Z (see Fig. 5) until its end portion lies parallel to the plane of the piece 4 from which it was struck. Its tip is spaced from the plate 3 by a collar 43 and held fixed to it by the screw 44. The feet 42 of the bridge piece 4 are secured to this same plate 3 Y sothat the bridge piece 4 is both internally and externally braced.V

The bridge flange 41 is slotted at 45 to receive the end I31 of the rack guide I3 of the rackspindle 9. The guide I3 is clamped by a set screw I3a in a clip block I3b which spans the stem 9. Ihe rack is thus guided within the bridge as well as at the upper and lower bearings I0 and II. These are carried by the casing and are axially aligned and aiord a new rack guide combination with the intermediate bridge piece 4 and its parts as before described.

Referring to Figs. 2 and 3, it will be seen that the bridge piece 4 interlocks in the assembly (see Fig. 7). The rack bar spindle 9 is guidedrin the opposed axial bearings Il] and Il. These are the usual bearings for this old type of dial gage. They assure complete alignment axially of the bridge piece 4. The rack bar spindle 9 carries the usual rack 9a which meshes with the pinion 60.

The upper bearing has been heretofore used as a dust cap clamp basis. This has some advantage and my invention utilizes it as a reasonable modification (see Fig. 9).- The dust cap IZ of Figs. 1 to 3 acts simply as a set screw as the obvious form of clamp is one of direct action as on the block or lock piece I4. This has usually been radially of the bezel ring. Figs. 1 to 3 show this old block form of outside clamp. Fig. 9 shows a new bezel assembly including an internal locking feature. In both instances the form shown is rigid but might be slightly resilient to yieldingly engage the knurled edge of the bezel ring 5.

In the form shown` in Fig. 9 the dust cap IZA common to this radial clamp type is'made with y a surrounding flange IZB. This cap is threaded on the upper bearing IDA which is surrounded as shown in Fig. 9 by a countersunk recess or lockway Ina. The bezel ring 5 is locked or un locked by simply screwing up on or unscrewing the dust cap lock member IZA.

This cap member lock IZA and the cooperating thread of the upper external spindle guide IBA are preferably made left handed according to my concept to make practically possible the ready adoption and use by'mechanics already habituated to a, right hand twist of the locking means in tightening as above described. I therefore 'J provide it for them in my structure by making the screw left handed. Otherwise, the dust caps I2 or IZA perform their usual duty in excluding dirt` from the bearing for the upper end of the spindle 9 which is normally positioned With'its stop screw 9c against the shoulder 9b. This acts as an extra seal when not in operation as the spring 'I0 draws down .on the guide I3 to which it is attached at one end. At its other end it is anchored to the casing I in a scallop like recess 'Il in the inner side of the casing wall, Where it is held by the screw 12.

The opposite end of the rack stem 9 carries the threaded anvil 90 which makes contact with the work in the usual manner but is interchangeable and replaceable.

My dial gages may be supported in any usual Way as by the ear 80 pierced for clamping as at 8| in any clamp or bracket;

end tosaid rack rod and having its other end guided in said slot.

2. The dial indicator of claim 1, said tongue being severed from said bridge piece by a U- shaped cut.

JAMES G. SISSON. 

